Breast cancer represents an internationally recognized public health concern, which often manifests itself in grave, and sometimes fatal, consequences for its victims. There is strong clinical evidence that breast cancer can be detected in its earliest stages, and that when found early, markedly improved results in morbidity and mortality are realized.
Mammography, clinical breast examination and breast self-examination are the current methods available for screening and early detection of breast cancer.
Mammography screening, although considered to be the “gold standard”, nevertheless suffers from well-known limitations including over-diagnosis. With optimal technique and patient conditions, it has a reported sensitivity between 69% and 90% and a specificity between 10% and 40%.
Many factors, including density of breast tissue (i.e., younger patients, implants, and post surgical state) can affect these values. Mammography, when used alone, is believed to miss between 10% and 30% of all breast cancers. Possible reasons may include density of breast parenchyma (as mentioned above), poor technique and positioning, error by the reading radiologist, and slow growing breast cancers. Although certain strategies, such as computer-aided detection (CAD) and/or rereading by another radiologist, have been implemented in certain cases, to improve overall detection capability, their impact on detection of breast cancer is variable, at best. Because the specificity of mammography for characterizing breast lesions is relatively limited, typically 50-75% of the identified abnormalities, when removed for biopsy analysis, are found to be benign.
Ultrasound has been used as an adjunct to mammography, and is of particular value in differentiating cystic from solid lesions and in facilitating guided biopsy of suspicious areas. However, ultrasound has inherent limitations, including the possibility of missing micro calcifications (associated with ductal carcinoma in situ (DCIS)) and difficulty in ensuring that the entire breast is imaged with the transducer.
These limitations have prompted investigators to examine the value of other imaging modalities such as scintigraphy, contrast-enhanced MRI and Magnetic Resonance Elastography (MRE) for tumor detection and characterization.
Magnetic resonance (MR)-guided biopsy is a critical element of any breast MR imaging capability to ensure optimal patient management. The preponderance of studies has demonstrated that this technique has high sensitivity (90-100%) for detecting breast cancer. This exceeds the sensitivity of any other imaging technology. While multiple studies have established that the sensitivity of MR-guided biopsy for diagnosing breast malignancy approaches 100%, the reported diagnostic specificity has been generally less favorable, ranging between 65% and 80%. Therefore, further improvements in the diagnostic specificity of MR-guided biopsy for diagnosing breast cancer is essential to maximize early detection and treatment. Specifically, identifying other, independent parameters effective for characterizing MRI-accessible tissue will permit enhanced differentiation of malignancy from benign breast lesions.
Magnetic Resonance Elastography (MRE) is a new technique useful for assessing the viscoelastic properties of tissue. The MRE technique can quantitatively depict the elastic properties of, e.g. breast tissues in vivo and reveal the high shear elasticity in known breast tumors. Sinkus and colleagues described the inversion techniques for breast MRE and applied the methods to study the mechanical properties of breast tissues in normal volunteers and patients with breast cancer.
The most obvious potential role for MRE in breast imaging is as a possible method for improving the diagnostic specificity of contrast-enhanced MRI. In order to determine whether or not MRE-based measurements of shear stiffness can improve the specificity of lesion classification in CE-MRI of the breast, in vivo testing would need to be conducted.
The instant inventors have previously designed breast gel phantoms and a piezoelectric motor driven needle driver for needle-guided breast MRE; developed an animal model with breast tumors and made use of the MRE driver at GE 1.5T and 3T MRI system.
The present invention provides an improvement over this previous work which utilizes an enhanced, drum driven needle-guided breast biopsy device, which is particularly constructed and arranged for utilization within an MRI machine, to generate shear waves, necessary to perform highly sensitive and specific MRE analyses, without generation of artifactual interference, due to the non-metallic nature of the device. Tests of this device have been carried out on human subjects at MRI Research Lab, Mayo Clinic, Rochester, and Jockey Club MRI Centre, The University of Hong Kong.
The overall objective of such testing is to demonstrate the ability of the instantly disclosed drum driven needle biopsy device to reduce unnecessary biopsies and interventions, by virtue of its increased sensitivity and specificity in diagnosing invasive breast cancer, especially in women with high hereditary risk.
Both mammography and MRI-guided breast tumor biopsies have been performed for more than 25 years, but neither technique is able to elucidate small cancers.
The instantly designed devices are at the forefront of technology in breast cancer diagnostics. Given the very high resolution provided by MRE images, the MRE needle-guided breast biopsy technique can detect small cancers (MRE generates high-amplitude, artifact-free motion throughout a breast to enable visualization of tumors of less than one hundred microns, a very small tumor, which is unable to be found by either MR-guided biopsy or mammography. The end-result of this technology will be the saving of additional lives, along with a reduction in the number of un-wanted biopsy procedures.
MRE surface drivers have previously been used for the detection of breast, liver, kidney and prostate tumors via generation of spherical waves and piezoelectric bending element driven MRE needle drivers have been used for the detection of breast, liver, kidney and prostate tumors by the generation of plane waves.
Currently, MRE surface drivers have certain limitations. Since they use relatively low frequency, the wavelength is relatively longer. The long wavelength makes it difficult to detect smaller lesions. The instant needle driver utilizes a much higher frequency range; therefore the wave length induced by the needle driver is much shorter than that induced by the surface driver. Additionally, since the needle deeply penetrates the tissue, lesions which are deeply located, or are smaller in size, are able to be detected.
By combining a combination of either acoustic, piezoelectric, electric, electro-mechanical or pneumatically driven surface drum drivers along with corresponding needle drivers, it is possible to generate both spherical and plane waves at the same time. The combined drivers can further improve the shear waves and increase the sensitivity and specificity for the detection of tumors, while again reducing unnecessary biopsies. Simultaneously, it is possible to use the needle to perform biopsies immediately after finding the lesion, thus eliminating an additional invasive step.
The instantly disclosed technology can be used on a variety of MRI machines, including, but not limited to those manufactured by General Electric, Siemens and Philips.
COMPARISON OF TECHNIQUESMR-guidedMRE needlebiopsybiopsyMR + MRESpecificity65-80%90%95%Adverse reactionYesNoYesto Gd-DTPASequence forNoYes—specimen imagingNeedle sizelargersmalllargerSmall cancerundetectabledetectable—